The major research objective is to develop the dynamic light scattering technique and to apply it to the study of some important biological systems. Two main areas application will be pursued: (1) The dynamics, structure and interaction of long rigid and semi-rigid rod-shaped biomacromolecules in solution and (2) The morphology and growth kinetics of some self-assembling systems, mainly surfactant micelles and phospholipid vesicles. The first area of application includes studies of the flexibility and hydrodynamic size of the myosin molecules from rabbit muscle and the amoeba Dictyostelium, the intramolecular relaxation modes of Lambda-phage DNA, and the interactions of rods (mainly short fragments of DNA) in solutions including the semi-dilute region, and also the low salt region in which there is evidence that extraordinary phases exist. The flexibility and solution interactions of another muscle protein, F-actin will also be investigated. Theoretical models for these systems will be constructed and used to aid in the interpretation of the experiments. In the second category, the morphology of phospholipid vesicles will be studied by a depolarized total intensity technique and the kinetics of vesicle fusion will be followed using a newly-developed inverse Laplace transform data analysis technique. Sphere-to-rod transitions in surfactant micelle systems will be followed using both polarized and depolarized, dynamic light scattering.